hypothalamus/pituitary Flashcards
anterior pituitary
adenohypophysis
- is of epithelial origin
- produce hormones in response to hormones from the hypothalamus delivered via the portal system of veins
- hormones released into the general circulation
- hypothalamus has indirect control through release of regulatory hormones
posterior pituitary
neurohypophysis
- is of neural origin
- contains axons originating from neurons in the hypothalamus
- these axons release hormones (oxytocin and vasopressin) directly into the general circulation
- neurosecretory
where does the thalamus, hypothalamus and epithalamus, embryonically develop from?
forebrain –> diencephalon
boundaries of the hypothalamus
anterior
- anterior commissure
- lamina terminalis
posteriorly
- mammillary bodies
- midbrain
superior
-thalamus
arcuate nucleus of the hypothalamus
- produces hypothalamic releasing factors
- contains DOPA-ergic neurons that inhibit prolactin release
preoptic area of the hypothalamus
- contains sexually dimorphic nucleus
- regulates release of gonadotropic hormones
structures making up the neurohypophysis
- median eminence
- hypothalamohypophyseal tract
- stalk
- posterior lobe
structures making up the adenohypophysis
- pars tuberalis
- anterior lobe
blood supply to the anterior pituitary
neurosecretory neurons release hormones into the superior hypophyseal artery at the median eminence.
The superior hypophyseal artery joins into the primary hypophyseal portal system, these capillaries join to form large vessels (hypophyseal portal veins) which spiral around the infundibulum down to the anterior pituiutary.
These portal veins then join to form a secondary capillary network, branching among endocrine cells
- superior hypophyseal artey
- primary plexus of hypophyseal portal system
- hypophyseal portal veins
- secondary plexus of hypophyseal portal system
- anterior hypophyseal veins
pituitary hormones
- FSH
- LH
- TSH
- adrenocorticotropic hormone
- prolactin
growth hormone
growth hormone
GH-RH released from the arcuate nucleus
GH-IH released from the periventricular nucleus of the hypothalamus
both released into the anterior lobe and cause the production of GH
GH acts on the liver to cause secretion of IGF-1
IGF-1 acts by stimulating growth of skeletal muscles, cartilage and many other tissues
it also feeds back to the stimulate GH-IH and inhibit GH-RH
prolactin and oxytocin
oxytocin = milk letdown
1.
prolactin
prepares mamillary glands for production
- can regulate its own synthesis and release from the anterior pituitary
- prolactin released from the ant pituitary gland acts back on the arcuate nucleus. Causing the release of dopamine in the median eminence
- dopamine has a negative feedback on prolactin
prolactin during lactation
switch from negative to postive feedback
- reduced dopamine secretion
- suckling stimulates
- E2 increases number and responisveness of lactotrophs
HPA axis
E2 feedback on GnRH neuronal network